Stabilizing absorption system



AWM M, MMU, J. A. CAMPBELL,

STABILIZING ABSORPTION SYSTEM Filed April 19, 1927 2 Shee`ts5heei w Mi;H93.; y J. A. CAMPBELL www@ STABLIZING ASORPTION SYSTEM Filed April-19.1927 '2, Sheets- Shen 2 Patented Apr. 1 5, 1930 13:44am-,v

PATENT- OFFICE JULIAN a. CAMPBELL, or LONG BEACH, CALIFORNIA.

s'rABILIzING Y, Ansonrrrorr SYSTEM v application mea vapril I9,

This inventan has to do primal-ny wat 5 stabilization are usuallyappliedto gasoline obtained by absorption from casing head gas and thefollowing specification will deal par' .ticularly with the invention asapplied to such gasoline, although in its general nature theinventionwill be seennot to be limited to such specific use, but capableof use for the stabilization of any gasoline, or in fact of anyadmixture of components of different boiling points, containing elementshaving boiling points lower, or vapor tensions higher, than is desirablein` the mixture. The gasoline obtained Vfrom casing head gas, commonlyby the absorption process, contains a fair proportion of'very volatileconstituents which are undesirable in commercial gasoline, the boilingpoint being very low and their vapor tension at ordinary temperaturesbeing very high. In operatingan absorption plant for a high percentageof recovery from natural gas it has been an inevitable concomitant thatthe absorption and recovery of these more volatile constituents has alsobeen increased. Consequently, the

resultant liquid has necessarily been subject to methods ofstabilization to remove these mostvolatile constituents; and, withoutgoing into detail, I may say that such processes and the attendantmechanisms of stabiliza-y tion have been more or less cumbersome andcomplicated and correspondingly expensive.

The general object of this invention is to;1 provide in an absorptionsystem a method.y

and apparatus arrangement whereby the ab-Y sorption system itself hasincorporated with- 10 in it meansY for eliminating the undesirablevolatile constituents, so that these 'volatile constituents are ejectedimmediatelyin the process of absorption and do not have to be removed bysubsequent operations, and. so

43 that the resultant absorption product is one that needs no furtherstabilizing. The results may be viewed as the effective combination ofstabilizing and absorption operations and apparatus, or may be viewed asthe combination, both as to method and apparatus, of

1927. Serial No. 184,868.

an absorption system and a dephlegmator the stabilization ofgasoline-that isthe-l removal from gasoline ofV undesirable andV highlyvolatile constituents.. Processes off system. All of these and otherobjects and' corresponding accomplishments will be best understood Vfromthe following specification wherein I explain vwhat is now my preferred'stabilizing-absorption system, reference for that purpose being had tothe accompanying drawings, in which Fig. l is a diagram illustrative ofa com\ plete 'system in accordance with my inven- 50 tion; i I ig. 2is adetailed section of the vapor separator which may optionally be used inthe system, that section being'taken as indicated by^`line 2 2 on Fig.1;65

Fig. 3 is a horizontal section as indicated by line 3 3 on Fig. 2;

Fig. 4 is a verticalview, with parts in elevation, of atypicalabsorption tower which may be used in the system; and 70 Fig. 5 is anenlarged horizontalsection on line 5*-5 of Fig. 4.

Describing vthe system in general and reer'ring first to Fig. 1, the.gas from the Well, known as natural gas or casing head gas, passesthrough pipe 10 to the absorption tower 11. Thevgeneral-function ofthisab- A sorption tower, as is well known, is to lalo-: i

sorb the vapors from the casing head gas i in a suitable absorbingmedium, usually a 30 fairly light petroleum product, leaving dry gas topass out through the outlet pipe 12,` the absorbent oil with its burdenof absorbed :constituents passing o ut as fat oil through pipe 13. Theoperation of the absorption 8.5

system, aside from the absorption tower, is

to separate the absorbed constituents -from the fat oil and to pass theresultant lean oil back to the absorber, the lean oil entering the.absorber through the pipe 14 and 90 passing down through the absorber incounter current against the rising laden gas which enters the lower endof the absorber. Typically the fat oil passes from the absorber first toa pump 16 which first pumps the fat 95 oil to a heat interchanger 17where the oil is somewhat warmed by heat exchange with the lean oilcomingfrom evaporator 18; thence through pipe 19 to a preheater 9 andthence,

in the usual installation, directly to evapora- 100.

tor 18 where the fat oil is finally raised to a tem erature sufficientto vaporlze and drive off all) of the absorbed hydrocarbon constituents,leaving the lean oil .to pass out through pipe 20 to heat exchanger y17and thence through pipe 21' to pump 22. From-pump -22 thelean'oil'passes throughpipe 23 to the coolin coil 24 where thetemperature of the lean o is reduced to the most eflicient point,usually around 65 or 70,o F.4 Thence the lean oil passes through pipe 14to the absorption tower as before stated. Y

y 4In my system, instead of passingthe pre- -heated fat oil directlyfrom preheat'er -9 toV evaporator 18 Ii'nay optionally pass itv throuv ha vaporv separator 25 -whose Vconstructlon and operation will behereinafter.

explained. In the broad aspects of my invention it is not necessary thatsuch a vapor sep- 'j sorption tower as shown inFig. 4 is one `(iearatorbe used, although -it maybe desirable in some instancest y y v Theabsorption operatlon 1n such an-abpendent for its over-all efficiencyupon vari; o us factors, such as the intimate contact of 5 the vaporladen gaswith the absorbing oil,

tion' during the absorption process. In suchj and also the generaltemperature of operaan absorber 'as shown 1n Fiv ."4 (this. absorber isexplained only as typica and not as 1a limitationuponthe invention)there are several perforated fioors andthe: lean absorbing oil, at atemratureof say F., is delivered to the-dl'stribut'ion'pipe 149 overtheuprinost.floor.'. The vapor laden gas--introu'oed through pipe 10 tothe lower end. of

.the absorber' is under a suicient pressureto bubble up through'the oilandthrough---the` rforated floors,lwhile the .oilflows down m floor tofloor, thus establishing'over each floor a layer or body of froth' inwhich 'the va r laden gas comes into intimatecon tact with the oil overa ver-y large total area 'l of contact. The froth over each 'floor'builds up until it reaches the upper edges of ans 31, the froth breakingup at the edges o -the1- pans,th`e clear oil with its burden oconstituents flowing over lthe-.edges of the pans and into themandthence'downzthrou'gh the standpipes 32to ints near the floor nextfbelow, to beagainA lrothed there bythe upwadly owin gas. The absorbingoil thus passes down t rough the tower in successive' stages while thegas bubblesu'p through the voil', the' oil and gas coming intosuccessive intimate contacts. The oil absorbs the absorbable vaporscarried by the incoming gas, andthe gas is correspondinglycleaned ofthose rva ors, `the percentage 'of absorption by the oi and cleaning ofthe gas, depending u n the relative point, so to speak, at which arption equilibrium is reached a's between the va r laden gas andtheabsorbing oil. Such'abgorption in practical operation of an absorptiontower is' not perfect, as it is im-l absorbed" practicable to reduce thetemperature of op eration, or increase the pressure of operation, to thepoint where the vapor tension of the substantially zero.' But it isendeavored to desirable constituents carried in the gas is 1 keep "thetemperature and pressure in the absorption tower at suoli points thatthe per- .centage of absor )tion of the desirable constituents is ma ecomparatively high, by maintaining conditions that lower the vaportension of the desirable constituents, and those same conditions loweralso the tempo- 1 rar vapor tension of the more volatile and unes'irable constituents and they are also absorbed in higher percentage.

conjunction with the absorption operation is based broadl upon theymaintenance Aof a lower portion o the absorbing body at a temperaturehigher than that of the upper ference'in'temperature may be maintainedin any suitable manner. For instance, as will readily berealized,thelower part of the absorbing oil body, streamer column, may be relativelyheated inlany suitable manner, as

'for instance, by steam coils or other Vwell known means.` Thelstabilizing operation depends fundamentally upon thus maintaining oftheoil` body Vand another part of the-oil body, that passfrst beingmai'ntainedatthe higher ternperature And ,such differential oftemperavture may of course be obtained by relatively cooling the part ofthe body that is to be vmaintained at a lower temperature. However, Iprefer, in absorption vprocesses-as now carried on, to relativel heatthe lower part of the absorbing oil bo y or stream, and to do 'that-byintroducing Warmer oil from'some suitable place 1n the system, becausethat can ',be done easilv and` effectively without loss of heat.'

I speak in a broad sense of ya body of absorbing oil, 'although in thecontinuous processes of' absorption as now practiced, thatA stream,

body is Ymaintainedfas a owin movingfdownwardly .through an a sorptiontower. However, it will be apparent from my description of operationthatmy stabilizing system is in generalapplicable to the older types ofabsorbing systems in which the .body ofabsorbing 'oil may be handled asa batch and not necessarily pass continuously through va downwardlymoving stream. But the continuous methodis preferred. So,

preferably I provide the typical stabilizing My method of accomplishingstabilization "portion of the absorbing body; and within the broadconcept of my invention this difa difference in temperature between onepart part ,through which laden gases iis tion tower depends uponseve'ral factors, including the temperature of thewarm oil thusdelivered to the tower and also including the nature of the constituentspresent in the orig- V inal gas and thenature of the desired na'lrecovery; However, to give anv idea of what may be apracticalarrangement I may say y of about130 F.; and lower down when thetemperature of the warmoil is correspondingly'higher. fat oilmay be thus'introduced at an intermediate point in` the absorber; and the diagramof Fig. 1 shows several arrangements which may `be used alternatively orin combination, or any or all-of which may be put into the plant'so asto be used alternatively or in combination. For instance, I show a valvecontrolled pip' 37 leading from lean oil pipe trolled pipe 38 leadin,'from lean oil pipe .20 to pipe35; also a va verontrolled pipe 39leading to pipe 35 and having branches 39*L and-39'? throu h which oilmay be introduced eitherfromt e Vfat oil pipe 19 or from the vaporseparator 25 (which typifies any point on the hot side-of the preheater9). It lean oil is introduced from pipe 23 just before the lean oilreaches coolingv coil 24, that oil will be at a temperature of about 130F., that being an average temperature at which the vlean oil leaves theheat interchanger 17.' If

the lean'oiL is introduced through pipe 35 from pipe 20 it will thenhave a temperature of about 320 F. in an average case and itsintroduction to the absorption tower as previously mentioned will belsomewhat lower down. If fat-oil is introduced through pipes 39 and 39bfrom a point between'the heat interchanger 17 'and preheater 9, it willhave a temperature of about 230 F. in an average case; while from the,vapor separator 25 through pipe 39b a fat oil will have an averagetemperature of about 320l F. l I shall first explain the operation ofthe system as if lean oil were introduced say from pipe 23 and at anaverage temperature of about 130 F. 4

In the Ordinar operation of the absorption tower as hereto ore explainedthe absorbing oil in the upper part of the tower has taken on a certainpercentage of the vaporous absorb, including a certain percentage of themost volatile and undesirable constituents and carries such percentagesof all constituents by the time it reaches an intermediate point in thetower. In normal operation, from there on down through4 the tower, theabsorbing oil absorbs` more of all the constituents; but the com arativepercentage absorption of the less vo -atile constituents is larger inthe lower part of the tower while Either warm lean oil or` warmshow avalve Acon thecomparative percentage absorption of the Y more volatileconstituents is larger in the `upper part-of the tower. Theabsorbing oilthereforetgoes downto the intermediate part of the tower fairly wellladen `with the most volatile constituentsyand it is there that thiscomparatively cool absorbing oil comesinto contact and is admixed withhotter absorbing oil, and the Whole body of oil from that point on downthrough the tower thus being subl stantially warmer than'pis the oil inthe upper part of the tower. vIn a typical 'case a suiicient quantity,of the hot oil may be run into the towerat the intermedia-te point toraise. the' temperature of the whole body of the oil .below .to about F.This warmer vlower body of absorbingA oil is still capable of absorbingthe less volatile and desirableconstituents and continuesso to do,although not in quite as high a percentage as would cooler oil under thesame circumstances. But the circumstances are further altered in this'lower warmer body of oil by the fact that the absorb of more volatileconstituents in that vwarmer f body is substantially wholly eliminated,as will be described, and this Warmer body of oil, thus being freed ofwhat would be its normal burden of most volatile constituents, again hasits' 'absorbing capacity for the less volatile constituents increased;so that the final absorbing eiciency of this lower body 1- of warmedoilis atleast not decreased, but may, as an actual matter of fact, bematerially increased as compared with standard-practices.

The temperature maintained in the lower warmer body of absorbing oil ishigh enough to vaporize the most volatile undesirable constituents andthose vapors are released from the warmeryoil andare carried upward inthe stream of gas that bubbles up through the upper cooler body of oil,When a condition of equilibrium is established-when the upper coolerbody of oil is loaded to its absorption capacity with these mostvolatile constituents,` then these volatile constituents begin to passout with the fixed gases at the upper end of the "absorben Thus innormal operation the absorber acts somewhat as does a dephlegf mator,wherein a higher temperature is maintained below than above, and thetendency in the upper part is toward condensation while the tendency inthe lower part is toward vavporization. That is also true in mystabiliz- ,tion of equilibrium, substantially no constitu- ,ents ofaboiling point lower than the temperature of the lower body of absorbingoil pass out with the absorbing oil through the final fat oil outlet.'By proper selection of relative 5 oil temperatures to suit any given setof conditions, the final absorption product can be kept substantiallyclean of the lightest and' undesirable constituents, while at the Sametime the absorption percentage of the heavier desirable constituents iskept very high.

-I have described a typical case whereA the warm oil is run into theabsorption tower 'at about its middle. However, this warm oil may be runinto the tower either higher up or lower down; and in some cases it maybe preferred to 1n]ect 1t into 'the tower at one of the lower absorblngfloors or'sections; and

it may be desirable to use less of. the hot oilV4 but to use itata-,higher temperature, so that the mixture is still mai-ntained at aboutthe same temperature ofabout 100F., mentioned hereinbefore. It will beunderstood, -of course, that this temperature of the'lower body ofabsorbing oil depends upon the liquids being absorbed. and upon thecharacter of the vapors and liquids desired to beeliminated from thefinal product.

- fat oil is usually yAnd'it is not necessary that the hot oil be allintroduced at one point in the absorber.

Typically the operation which I here describe Y (distributed points.along the height ofthe'- -tower. For instance, the tower may beprovided with a distribution pipe 36 directly over 'theuppermostfloorand others, as dndicated in Fig. 4, may be spaced down through theheight of the tower, and a proportionate amountiof hot oil be. put in ateach of these distributionpoints or -at any selected ones. Thus 4thetemperature of the oil body as itvflows down through the tower may begradually raised, and the`amount of stepup in temperature betweensuccessive floors may be either uniform or non-uniform, asmay be foundmost desirable and efficient. e

In any usual absorption system where the preheated, as by a preheater 9,and althou the pressure maintained by pump 16 may e fairly high, acertain amount of vapor is generated and it may be desirable inany'system to take that vapor off before the preheated oils are put intoevaporator 18, where a. still higher ten perature is, maintained. Thereis no obj ct inputting the vapors themselves into the evaporator andtheir presence in the evaporator merely decreases vthe eiciency ofits'operation in heatrature, as before explained, or may4 ing theremaining liquid. In any system these vapors contain very largely thelightest undesirable constituents and their separation at that point andtheir return, as for instance through pipev 40, to-the bottom ofthe'absorption tower will in some instances further decrease thepercentage of such very light vapors put through thezevaporator; andthus put into the final product which passes out from the evaporatorthrough vapor line4l to de- )hlegmator 42 and thence to condenser 43.

n my system the use o'fjsuch a separator, with the return of theseparated lightest vapors to thevbottom of the absorption tower, removesfrom the final product practically all the remaining parts of thelightestl undesirable constituents. It will be understood that preheater9 is usually run at such a temperature, sayBQOfJ F., that it will alwaysevaporate all of these lightest constituents and usually some of theheavier ones. All 4these vapors, interme iate section ofthe absorptiontwer, passup through the 'tower along with the 'original gases andvapors, and again go through the absorption and stabilizing operaut backint'o' the Jbottom or vsome tion, the lightest vapors finally passingoutv with the dry gases, and the heavier vapors being reabsorbed.`

, In reintroducmg vthe gases andpva'pors through line 40, .to theabsorption tower, in

lmy system I find it best vto introduce them y at an mtermediate pointinthe tower, preferably so that they will not come into contact with thehottest part of the oil body. I

find that if these-:gases and vapors are 'introduced at the bottom ofthel tower, by com-- ling into contact/with the hottest oil-,they

'substantially reduce the-absorption capac ity of that hot eilasregardsthe desirable absorbed constituents', and the recovery efficiencyof the'tower as a Whole is thus kept down. By introducing 'thegasesand-vapors at an intermediate point, as at the point where thepipe-1() is shown 'coming into the absorber in Figlf'fl, above theintroduction of the warm oil, or'lqabove the'hottest part of theabsorbing oil'body, the desirable features of reintroduetion areattained'andthe absorbing action is' kept Aup to its highesteflicie'ncy. The' result is to clean the absorbmg oil most completely ofthese lightest constituents before itfg-passes tothe evaporator,

with the result that the final asoline condensed at 43 is substantiallyentirely clean of the light undesirable fractions.,

Such avapor separator may consist of an apparatus as shown in Figs. 2and 3. The

vapor sep'aratorymay comprise a shell 45 with a number of -superposedannular pans 46 having perforated', b ottoms, the pans being preferablyspacedf-,from the separator shell and preferably having central 4openings 47 through whicfinthe vapors may rise upwardly., The' heatedoils rom the preheater are introduced through pipe 19a to 'a distributor47 in the' uppermost pan. The oil lflows out to form alayer, and showersdown through the perforated bottom into the next pan, and so on untilthe oil finally reaches the bottom of the shell, where the body of oilis maintained constantly at 48 by the actionof a fioat 49 controlling anoil outlet valve 50 in line 19b which goesto evaporator 18,"The'vaporsare released from the oil during the showering and, passingtothe upperpart of the shell, go out through theA vapor line 40 undercontrol of valve-51 to the bottom or some intermediate section of theabsorption tower. Valves 50 and 51 are both operated by float 49,`thearrangement'being such that as valve 50 is opened valve 51 is closed,and vice-versa.

The valves illustrated are ofthe simple type' l movement upwardly of oat49 will open valve-50 and will close valve 51. The purpose of thisarrangement is to keep suflicient vapor pressure on the oils to forcethem into the evaporator and at the same time to release the gases andvapors as they areliberated from the oil. In practice the valvemechanism establishes a position of equilibrium in which both valvesVare somewhat open and sufficient pressure is at thesame time maintainedto force theoil out, the body of oil above outlet pipe 19h serving toprevent vapors passing out through that line.

Althoughl it is preferable from some standpoints to utilize clean oil inthe lower part of the absorption tower, fat oil can be used there Vandthe system makes provision for using fat oil if desired. The generaloperation with fat oil is substantially the same as with lean oil; it isexactly the same as far as the refluxing and stabilizing operations areconcerned, being only dierent in that the absorption action in the lowerpart of the tower is somewhat cut down due to use there of a certainamount of oil which is already more or less saturated with absorbedcomponents.

It may be mentioned that should heated liquid, comprised ofconstituentswithin the volatility range of the vapors, be introduced tothe lower part of the absorption tower, the interaction between theheated liquid and vapors would be fundamentally the same as in thedescribed system wherein the absorbing liquid is otl comparatively lessvvolatility, that is, supposing the hot oil introduced through line 35consisted inu certain comparatively v heavy fractions finally .derivedfrom the vavapors would take place in the downward flowing oil,accompanied by vaporization of lighter fractions therein. Due to. thecomparative volatility ot the lighter o il over the its ultimate effect,be mainly one of rectification, althoughthis rectification may beconsidered as occurring through the stabilizing of the absorption ofthevapors in the lighter liquid, and which stabilization is efficientlycarried out according to the present method.

`l. A method of stabilizing the absorption, in an absorbing liquid, ofliquids having dif- .ferent vapor tensions, the operation of absorptionconsisting in passing Vapor laden gases upwardly through a downwardlymoving stream of absorbing liquid, then heat-ing. the laden absorbingliquid to vaporize oli the absorbed liquids, and then cooling andreturning the lean absorbing liquid to said stream; that includesmaintaining the lower part of said absorbing stream at a temperaturehigher than that of the upper part by introducing into the lower part ofsaid stream a certain amount of the heated absorbing liquid. Y

2. A method of absorbing and stabilizing liquids having different vaportensions, that includes passing vapor laden gases upwardly through adownwardly moving stream of absorbing liquid, removing the ladenabsorbing liquid from the lower end of the stream and heating it tovaporize ofi' its absorbed liquids, and maintaining the lower part ofsaid absorbing liquid stream at a higher temperaliquid from the lowerend ofthe stream and heatingv it to vaporize ofi' its absorbed liquids,separating the vapors of the absorbed liquid from the absorbing liquid,cooling the absorb` ing liquid and .returning -it4 'to said Vstream andmaintaining the lower part of said stream at a higher temperature thanthe upper part `by introducing into the lowerxpart of said stream aportion of the heated lean absorbing liquid as it comes from thevaporizing and separating operation.

4. Apparatus for the method herein described, comprising an absorptiontower having means for introducing a lean absorbing liquid at its upperend and -vapor laden gas at its lower end, means for taking off dry gasat its upper end and laden absorbing liquidat its lower end, means forheating the laden absorbing'liquid to evaporate there- `from theabsorbed liquids, means to cool the lean absorbing liquid resulting fromsaid vevaporation and to return it to the UPPSI end of the absorptiontower, and means for introducing a portion ot' the heated absorbing itermediate point inthe absorption tower.

end of t e absorption tower, means for taking olf a portion of the leanabsorbing liquid as itv comes heated from the vevaporation means andintroducing said portion to an in- 6. Apparatus for the method hereindescribed, comprising an absorption tower hav-l ing means forintroducing a lean absorbing liquid at its upper end and vapor ladengas.

at its ,lower end, means for taking oil' dry gas at its upper end andladen absorbing liquid at Vits lower end, means for heating the ladenabsorbing liquid to a temperature suiiicient to y heat introduction'.

9. The method of .absorbinga'nd vaporize off the more volatile of itsabsorbed liquids, means for separating the vapors produced by saidheating and return them to an "wardly lthrough a downwardly movingstr'eam'of absorbing liquid, supplying heat from an extraneous' sourceto the lower portion'v of l'said .downwardly moving stream above thepoint of gas introduction thereto, whereby the lower portion ot' thestream is maintained at a comparatively higher temperature than theupperpart.

l0. rI he method otabsorbing and stabilizing liquids having dierentvapor tensions, that includes passing vapor laden gases lupwardlythrough a downwardly moving stream of absorbing liquid, maintaining thelower portion of said downwardly moving 'stream above the point ot' gasintroduction thereto, at a comparatively higher temperature than theupper port1on of the stream, and

' with a relatively abrupt change in temperature at the upper and lowerends of said low- .er and upper portions, respectively, of' the stream.

In witness that I claim the foregoing I have hereunto subscribed my namethis 29 day of March, 1927. y

t JULIAN A. CAMPBELL.

intermediate point of the absorption tower,

and means for introducing a portion of the heated 'absorbing liquid toan intermediate point in the absorption tower. v

7. The method of* tabilizing the absorption, in an absorbing liquid, ofliquid having diierentvapor tensions, the operation of absorptionconsisting in passing vapor laden gasesupwardly through a downwardlymovlng stream of absorbing liquid, lthat includes supplying heat from anextraneous source t0 the downwardly moving liquid at an intermediatepoint in said stream and above the the lower part of said gas contactingliquid stream is maintained at a temperature higher than that of-theupper part of said stream with a relatively abrupt change in temperatureat the point of heat introdueion.

8. The'method of absorbing and stabilizing liquids having diferent vapprtensions, that include passing vapor laden gases upwardly through adownwardly moving stream of absorbing liquid, supplying heat from anextraneous sour'ce to the downward ly moving liquid at -an intermediatepoint in said stream above the point of gas introduction thereto,whereby the lower part of said point of gas introduction thereto,whereby A I gas contacting liqui'dstream is maintained at a temperaturehigher than that of the upper part of said stream with a relativelyabrupt change in temperature at .the point of "statuizing liquids havingdifferent vapor tensions, that includes passingv vapor laden gases up-

